[PATCH] x86/mm: Limit 2/4M size calculation to x86_32

[Stefan Bader]

Avi wrote:
>The fact that the check is only done on i386 and not on x86_64
> may come from one of
>
> - an oversight
> - by the time x86_64 processors came along, the problem with
>   conflicting sizes was resolved
> - the whole thing is bogus
>
> Copying hpa who may be in a position to find out which.

Talking to hpa it is more of the last. For more than just this
reason. Since the whole area of initial page tables seems to be
rather sensitive and easy to break there have been discussions
and plans to come up with a rewrite to improve on all those
shortcomings.

The detail I am not agreeing with hpa is the fixup for the
immediate breakage at head. IMO right now the code just has
regressed and that should be fixed as soon as possible.
Plus doing a specific and small fix allows that to be applicable
to stable (which again still depends on things being upstream).

Hence the re-send in the hope that on the larger scale the may
be agreement on the immediate fix. I am not doubting the usefulness
or need of a better solution, but I think that having a remedy of
the current situation just until then has enough benefit to be
considered.

-Stefan